Particularly in industrial applications, it is important to minimize the floor space occupied by manufacturing equipment. Thus it is important that such equipment be as compact as possible. Additionally, such manufacturing equipment typically requires periodic maintenance or component replacement. For required maintenance and/or component replacements, it is important to minimize the equipment down-time. Therefore it is desirable to facilitate access to internal components in a compact and often congested configuration with minimal disassembly and reassembly. In accordance with the conventional art, this usually necessitates a design compromise between compactness and access. For example, in a compact apparatus there is often essentially zero clearance for needed access to a component.
FIG. 1A is a partial cross-sectional view of an optical shutter assembly for use with a laser and will be designated as equipment 10. Equipment 10 has a housing 12 mounted between two plates 14 and 16 with essentially zero clearance. Equipment 10, not including a seal, will later be contrasted with similar equipment in FIG. 1B including a seal. With equipment 10 fully assembled, openings 13 and 15 in housing 12 and plate 14, respectively, are accurately aligned. To remove housing 12, it may be necessary first to remove plate 16 from housing 12, and then to remove housing 12 from plate 14. Optionally, it is possible to detach housing 12 from both plates 14 and 16 and then remove housing 12 slidably parallel to plates 14 and 16, as indicated by arrows 18.
Mechanical seals, including fluid seals, gas seals, pressure seals, and vacuum seals, are widely used in a variety of applications. Materials commonly used as sealing surfaces include metals, plastics, foams, and elastomers. Seal configurations include, for example flexible o-rings or gaskets, which are typically deformed under compression to provide a seal between two or more solid surfaces. Many seals are used to prevent a fluid or fluids, for example air and/or other gas, from leaking into or out of an enclosure. In lasers and optical systems, particularly gas lasers, seals are typically required. Conventional seal configurations include o-ring face seals, o-ring gland seals, and gasket seals, formed for example of metal, elastomer, and/or foam materials.
FIG. 1B is a partial cross-sectional view of equipment 20 similar to equipment 10 of FIG. 1A, but including a sealed interface. Equipment 20 includes a housing 22 mounted between plates 24 and 26 with essentially zero clearance. With equipment 20 fully assembled, openings 23 and 25 in housing 22 and plate 24, respectively, are accurately aligned. Additionally, equipment 20 includes a seal assembly 27 at the interface between housing 22 and plate 24, which prevents leakage of fluid around the edges of openings 23 and 25. A sealed chamber 40 isolated from exterior 50, is thereby formed internal to housing 22. Typically sealed chamber 40 extends through openings 23 and 25 in an upper extension 42, indicated by dashed lines in FIG. 1B. Likewise sealed chamber 40 optionally extends through corresponding openings in plate 25 in a lower extension 44, also indicated by dashed lines in FIG. 1B. Conventionally, seal assembly 27 is attached to housing 22 and includes a bezel ring 28 that protrudes into opening 25 in plate 24. Optionally, seal assembly 27 is attached to plate 24, and bezel ring 28 protrudes into opening 23 in housing 22. Protruding bezel ring 28 prevents the removal of housing 22 slidably relative to plates 24 and 26 of equipment 20. Therefore, in accordance with the conventional art, housing 22, including a seal assembly 27, can be removed from equipment 20 only by first removing plate 26 or 24.
Housing 22 is an optical shutter housing mounted with essentially zero clearance between two parallel plates 24 and 26 of an ultraviolet (UV) excimer laser system (see for example U.S. application Ser. No. 08/900,203, filed Jul. 24, 1997, which is incorporated herein by reference in its entirety). Accurately aligned openings 23 and 25, which accommodate the laser beam path, are provided in shutter housing 22 and in at least one plate 24, respectively. Seal assembly 27 prevents UV radiation from escaping and confines pure nitrogen gas used to purge oxygen from the beam path. Oxygen could otherwise corrode optically coated surfaces or form ozone under UV irradiation. Seal assembly 27 typically comprises a silicone foam rubber gasket 30 compressed between a counterbore 32 in plate 24 and protruding bezel ring 28 attached to shutter housing 22. This configuration further prevents direct emanation of reflected or scattered UV radiation. However, protruding bezel ring 28 necessitates removal of a plate 24 or 26 before shutter housing 22 can be removed. This is a time consuming process, which is particularly undesirable in an industrial environment.
Needed in the art is a seal configuration and method of sealing that accommodate tolerance variations and provide a combination of seal integrity, optimum equipment compactness, and efficient accessibility for maintenance and component replacement, particularly relating to industrial apparatus, and more particularly relating to laser and optical equipment.